Package org.jgroups

Class NioMessage

java.lang.Object
org.jgroups.BaseMessage
org.jgroups.NioMessage
All Implemented Interfaces:
Constructable<Message>, Message, SizeStreamable, Streamable
public class NioMessage extends BaseMessage
A Message with a (heap-based or direct) ByteBuffer as payload.

Note that the payload of an NioMessage must not be modified after sending it (ie. JChannel.send(Message); serialization depends on position and limit to be correct.

Since:
5.0

  • Field Details

    • buf

      protected ByteBuffer buf
      The payload

    • use_direct_memory_for_allocations

      protected boolean use_direct_memory_for_allocations
      If true, use direct memory when creating ByteBuffer payloads, e.g. on setArray(byte[], int, int), setArray(ByteArray), setObject(Object) or when getting read from the network (readPayload(DataInput)).

      Unless this flag is set to true, a direct ByteBuffer payload will become a heap-based payload by a receiver when sent over the network. This may be useful if we want to use off-heap (direct) memory only for sending, but not receiving of messages.

      If we want the receiver to create a direct-memory based message, set this flag to true before sending the message.

  • Constructor Details

    • NioMessage

      public NioMessage()

    • NioMessage

      public NioMessage(Address dest)
      Constructs a message given a destination address
      Parameters:
      dest - The Address of the receiver. If it is null, then the message is sent to all cluster members. Otherwise, it is sent to a single member.

    • NioMessage

      public NioMessage(Address dest, ByteBuffer buf)
      Constructs a message given a destination and source address and the payload byte buffer
      Parameters:
      dest - The Address of the receiver. If it is null, then the message is sent to all cluster members. Otherwise, it is sent to a single member.
      buf - The payload. Note that this buffer must not be modified (e.g. buf[0]='x' is not allowed) since we don't copy the contents.

  • Method Details

    • getBuf

      public ByteBuffer getBuf()
      Returns the byte buffer. Do not read from/write to it, or else retransmissions will fail! Use ByteBuffer.duplicate() before, to create a copy, if the buffer needs to be read from

    • setBuf

      public NioMessage setBuf(ByteBuffer b)

    • create

      public Supplier<Message> create()
      Description copied from interface: Constructable
      Creates an instance of the class implementing this interface

    • getType

      public short getType()
      Description copied from interface: Message
      Returns the type of the message, e.g. BYTES_MSG, OBJ_MSG etc

    • useDirectMemory

      public boolean useDirectMemory()

    • useDirectMemory

      public NioMessage useDirectMemory(boolean b)

    • hasPayload

      public boolean hasPayload()
      Description copied from interface: Message
      Returns true if the message has a payload, e.g. a byte[] array in a BytesMessage or an object in an ObjectMessage. This is more generic than Message.hasArray(), as it is not just applicable to a byte array.
      Returns:
      True if the message has a payload

    • hasArray

      public boolean hasArray()
      Description copied from interface: Message
      Returns true if this message has a byte[] array as payload (even if it's null!), false otherwise

    • isDirect

      public boolean isDirect()

    • getOffset

      public int getOffset()
      Description copied from interface: Message
      Returns the offset of the byte[] array at which user data starts. Throws an exception if the message does not have a byte[] array payload (if Message.hasArray() is false).

      Note that this is a convenience method, as most messages are of type BytesMessage.

    • getLength

      public int getLength()
      Description copied from interface: Message
      Returns the length of the byte[] array payload. If the message does not have a byte[] array payload (Message.hasArray() is false), then the serialized size may be returned, or an implementation may choose to throw an exception

    • getArray

      public byte[] getArray()
      Description copied from interface: Message
      Returns a reference to the payload (byte array). Note that this array should not be modified as we do not copy the array on copy() or clone(): the array of the copied message is simply a reference to the old array.

      Even if offset and length are used: we return the entire array, not a subset.

      Throws an exception if the message does not have a byte[] array payload (Message.hasArray() is false).

      Note that this is a convenience method, as most messages are of type BytesMessage. It is recommended to downcast a Message to the correct subtype and use the methods available there to get/set the payload.

    • setArray

      public NioMessage setArray(byte[] b, int offset, int length)
      Sets the internal buffer to point to a subset of a given buffer.

      Note that the byte[] buffer passed as argument must not be modified. Reason: if we retransmit the message, it would still have a ref to the original byte[] buffer passed in as argument, and so we would retransmit a changed byte[] buffer !

      Parameters:
      b - The reference to a given buffer. If null, we'll reset the buffer to null
      offset - The initial position
      length - The number of bytes

    • setArray

      public NioMessage setArray(ByteArray b)
      Sets the buffer

      Note that the byte[] buffer passed as argument must not be modified. Reason: if we retransmit the message, it would still have a ref to the original byte[] buffer passed in as argument, and so we would retransmit a changed byte[] buffer !

    • getObject

      public <T> T getObject()
      Description copied from interface: Message
      Gets an object from the payload. If the payload is a byte[] array (e.g. as in BytesMessage), an attempt to de-serialize the array into an object is made, and the object returned.

      If the payload is an object (e.g. as is the case in ObjectMessage), the object will be returned directly.

    • getObject

      public <T> T getObject(ClassLoader loader)
      Tries to unmarshal the byte buffer payload into an object
      Returns:
      The object

    • setObject

      public NioMessage setObject(Object obj)
      Takes an object and uses Java serialization to generate the byte[] buffer which is set in the message. Parameter 'obj' has to be serializable (e.g. implementing Serializable, Externalizable or Streamable, or be a basic type (e.g. Integer, Short etc)).

    • copy

      public NioMessage copy(boolean copy_payload, boolean copy_headers)
      Create a copy of the message.

      Note that for headers, only the arrays holding references to the headers are copied, not the headers themselves ! The consequence is that the headers array of the copy hold the *same* references as the original, so do *not* modify the headers ! If you want to change a header, copy it and call BaseMessage.putHeader(short,Header) again.

      Specified by:
      copy in interface Message
      Overrides:
      copy in class BaseMessage
      Parameters:
      copy_payload - Copy the buffer
      copy_headers - Copy the headers
      Returns:
      Message with specified data

    • size

      public int size()
      Description copied from interface: Message
      Returns the exact size of the marshalled message
      Specified by:
      size in interface Message
      Overrides:
      size in class BaseMessage
      Returns:
      The number of bytes for the marshalled message

    • toString

      public String toString()
      Overrides:
      toString in class BaseMessage

    • copyPayload

      protected Message copyPayload(Message copy)
      Description copied from class: BaseMessage
      Copies the payload
      Overrides:
      copyPayload in class BaseMessage

    • sizeOfPayload

      protected int sizeOfPayload()

    • writePayload

      public void writePayload(DataOutput out) throws IOException
      Throws:
      IOException

    • readPayload

      public void readPayload(DataInput in) throws IOException
      Throws:
      IOException

    • createBuffer

      protected ByteBuffer createBuffer(byte[] array, int offset, int length)